This invention relates to oil-submerged sliding members used in oil, and particularly to oil seal rings formed from the oil-submerged sliding members.
Automatic transmissions for automobiles such as torque converters and hydraulic clutches have oil seal rings at necessary locations to seal hydraulic oil therein. Such oil seal rings are rotatably mounted between a rotary shaft and a cylinder while kept in sliding contact therewith. It is therefore required that such oil seal rings have a low friction coefficient, high wear resistance, a low tendency to damage a cylinder (mating member) to be brought into sliding contact, good oil sealing properties and other properties. Conventional oil seal rings of this type were made of cast iron. Efforts have been made to develop materials for seal rings which can prevent oil leakage even if used in today's compact, lightweight, high-performance hydraulic devices. Now, an increasingly large number of oil rings are made of tetrafluoroethylene resin, a material which is superior in sealing and sliding properties to cast iron.
Cast-iron oil seal rings are high in wear resistance and less likely to abrade a ferrous mating member, but poor in sealing properties. On the other hand, tetrafluoroethylene rings, superior in sealing properties, tend to wear out quickly as the PV value increases.
In Unexamined Japanese Patent Publications 55-7848, 2-175793 and 7-179846, various oil seal rings that have good sealability are disclosed.
The oil seal rings disclosed in these publications are all intended for use with mating members made of soft materials such as aluminum alloy. If such seal rings are used with a non-soft ferrous mating member, the mating member may abrade the seal rings, causing oil leakage, though the mating members are abraded little.
An object of this invention is to provide an oil seal ring which is made from a material which is injection-moldable and thus advantageous for mass-production, and which can be used with either a soft or a non-soft mating member.